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The porcelain crab Neopetrolisthes resembles a crab, but is more closely related to squat lobsters and hermit crabs.

In evolutionary biology, carcinisation (or carcinization) is a hypothesised process whereby a crustacean evolves into a crab-like form from a non-crab-like form. The term was introduced by L. A. Borradaile, who described it as "one of the many attempts of Nature to evolve a crab".[1]

Carcinisation is believed to have occurred independently in at least five groups of decapod crustaceans, most notably king crabs,[2] which most scientists believe evolved from hermit crab ancestors. The other examples are the family Porcellanidae, or porcelain crabs (which are closely related to squat lobsters),[3] the hairy stone crab Lomis hirta, the coconut crab Birgus latro, and true crabs.[4] The example of king crabs (family Lithodidae) evolving from hermit crabs has been particularly well studied and, although some doubt this theory, there is considerable evidence in its favour. For example: most hermit crabs are asymmetrical, so that they fit well into spiral snail shells; the abdomens of king crabs, even though they do not use snail shells for shelter, are also asymmetrical.[5][6][7][8]

An exceptional form of carcinisation, termed "hypercarcinisation", is seen in the porcelain crab Allopetrolisthes spinifrons.[9] In addition to the shortened body form, A. spinifrons also shows similar sexual dimorphism to that seen in true crabs, where males have a shorter pleon than females.[9]


  1. ^ Patsy A. McLaughlin & Rafael Lemaitre (1997). "Carcinization in the anomura – fact or fiction? I. Evidence from adult morphology". Contributions to Zoology 67 (2): 79–123.  PDF
  2. ^ Jonas Keiler, Stefan Richter & Christian S. Wirkner (2013). "Evolutionary morphology of the hemolymph vascular system in hermit and king crabs (Crustacea: Decapoda: Anomala)". Journal of Morphology 274 (7): 759–778. doi:10.1002/jmor.20133. 
  3. ^ Jonas Keiler, Stefan Richter & Christian S. Wirkner (2014). "Evolutionary morphology of the organ systems in squat lobsters and porcelain crabs (Crustacea: Decapoda: Anomala): an insight into carcinization". Journal of Morphology. doi:10.1002/jmor.20311. 
  4. ^ C. L. Morrison, A. W. Harvey, S. Lavery, K. Tieu, Y. Huang & C. W. Cunningham (2001). "Mitochondrial gene rearrangements confirm the parallel evolution of the crab-like form" (PDF). Proceedings of the Royal Society B: Biological Sciences 269 (1489): 345–350. doi:10.1098/rspb.2001.1886. PMC 1690904. PMID 11886621. 
  5. ^ C. W. Cunningham, N. W. Blackstone & L. W. Buss (1992). "Evolution of king crabs from hermit crab ancestors". Nature 355 (6360): 539–542. Bibcode:1992Natur.355..539C. doi:10.1038/355539a0. PMID 1741031. 
  6. ^ Patsy A. McLaughlin, Rafael Lemaitre & Christopher C. Tudge (2004). "Carcinization in the Anomura – fact or fiction? II. Evidence from larval, megalopal and early juvenile morphology". Contributions to Zoology 73 (3): 165–205. 
  7. ^ Ling Ming Tsang, Tin-Yam Chan, Shane T. Ahyong & Ka Hou Chu (2011). "Hermit to king, or hermit to all: multiple transitions to crab-like forms from hermit crab ancestors". Systematic Biology 60 (5): 616–629. doi:10.1093/sysbio/syr063. PMID 21835822. 
  8. ^ Rafael Lemaitre & Patsy A. McLaughlin (2009). "Recent advances and conflicts in concepts of anomuran phylogeny (Crustacea: Malacostraca)" (PDF). Arthropod Systematics & Phylogeny 67 (2): 119–135. 
  9. ^ a b Alexandra Hiller, Carlos Antonio Viviana & Bernd Werding (2010). "Hypercarcinisation: an evolutionary novelty in the commensal porcellanid Allopetrolisthes spinifrons (Crustacea: Decapoda: Porcellanidae)" (PDF). Nauplius 18 (1): 95–102.